Radial-flow-compressor



Feb. 23, GARVE 2,925,952

RADIAL-FLOW-COMPRESSOR Filed June 25, 1954 2 Sheets-Sheet l ALEXANDERGARVE WMM 9% ATTGRN EYS Feb. 23, 1960 A. GARVE 2,925,952

RADIAL-FLOW-COMPRESSOR Filed June 25, 1954 2 Sheets-Sheet. 2

INVENTOR ALEXANDER GARVE flwwzauzmmz ATTORNEYS I United Sates Patent 62,925,952 RADIAL-FLQW-COMPRESSOR Alexander Garve, Augsburg, Germany,assignor to Maschinenfabrik Augsburg-Numberg A.G., Augsburg, Germany, acorporation of Germany Application June 25, 1954, Serial No. 439,350

Claims priority, application Germany July 1, 1953 Claims. (Cl. 230-127)This, invention relates to radial-flow compressors such as gas and aircompressors and the like, and more particularly to the construction,dimensioning, and configurations of inlet, discharge and collectingchannels for radial flow compressorsj -It has been discovered that theoperating efliciencies of radial flow compressors can be substantiallyincreased and the over-all size and complexity reduced by the properconfiguration and dimensioning of the various inlet, discharge, andcollecting channels through which the medium being compressed flows bothbefore and after contact with the compressor rotor. Such compressorsinclude particularly the radial flow type in which the air or othermedium to be compressed flows into the compressor adjacent the center ofthe compressor rotor, is worked upon by the rotorblades, and isdischarged around theperiphery of the rotor and collected in acollecting channel under pressure to be led off to do work. Particularlywith radialflow compressors in applications such as airplane engines andthe like, the ,efliciency of the compressor and the overall size thereofmay be of great importance. According to this invention, the advantagesof sub-. stantially higher efliciencies; and reduced size are obtainedby providing'an inlet channel of substantially diminishingcrosssectional area to deliver the air, or gas or other mediumvto, becompressed to the rotor adjacent the center thereofa Also a dischargechannel of diminishing cross sectional area is, provided at thedischarge side of therotor, and a spirally. configured collectingchannel of noncircular andincreasing cross section is provided aroundtherotor to enhancethe rectification and unification of .the variousdirections of flow of the air or other medium being discharged by therotor under pressure as well as the conversion of various velocitycomponents of the flowing medium into pressure energy with a minimum ofenergy loss.

- It is accordingly an object of the present invention to provide aradial flow compressor of the character described, having inlet anddischarge channels of gradually diminishingncross section along the lineof flow therethrough and a, spirally disposed collecting channel ofgradually increasing noncircular cross section arranged axially to oneside of the radial plane of the discharge side of the rotor. H r v Afurther object of'this invention is to provide in a radial flowcompressor of the character described an inward jog or suddensubstantial constriction of the inlet radial-flow compressor of thecharacter described a discharge channel of a length which is keptconsistent with constructional limits and increased efiiciency yet islong enough to avoid the production of undue noise from the 2,925,952Patented Feb. 23, 1960 discharge thereinto of the working medium underpressure.

Still another object of this invention is to provide in a radial-flowcompressor of the character described a spiral collecting channel with anoncircular cross section for increased efliciency in the conversion ofvelocity energy to pressure energy therein and means for offsetting thecollecting channel from the radial plane of discharge by the rotor.

A still further object of the present invention is to provide in aradial-flow compressor of the character described a spiral collectingchannel in which the axial and radial dimensions of the cross sectionsthereof are coordinated with the orientation of the channel with respectto the radial plane of discharge from the rotor and the diameter of thespiral in which the channel lies to provide for maximum efficiency withminimum space requirements and constructional complexity.

Other objects and advantages of this invention will be apparent from thefollowing description, the attached drawing and the appended claims.

In the drawing,

Fig. 1 is an axial section through a compressor embodying thisinvention; and

Fig. 2 is a view partly in elevation and partly in section along theline II--II of Fig. 1.

In order better to understand this invention and the application of theteachings thereof to radial-flow compressor design, consideration of anumber of factors concerning the flow of the air or other medium throughthe compressor may be helpful. Considering, for example; radial flowcompressors in which the gas or other medium to be compressed isintroduced in an axial direction adjacent the center of the rotor andthereafter passes radially outwardly among the rotary blades to bedischarged at the periphery of the rotor, it will be apparent that theworking medium undergoes a number of changes in direction andspeed withconcomitant variations in velocity, energy, and pressure. Thus,initially, the axially directed medium is contacted by the blades, givena rapid circumferential motion as well as being moved radially outwardlyby the blades. Upon discharge at the periphery of the rotor underpressure, both velocities and directions of flow are again altered bythe collecting conduits, etc.

The efiiciency of the compressor, of course, depends considerably uponthe extent to which these several alterations in direction of flow andvelocity can be accomplished without loss of energy within thecompressor. If it is attempted to control and utilize to a maximumextent the various flow characteristics of the working medium throughthe compressor merely by variations in the blade settings and designand/or the suitable dimensioning of the flow channels through the bladesthemselves, the best results are not obtained. Accordingly, the presentinvention concerns itself with the flow characteristics and energyrelationships in the various flow channels before and after the rotor.

It has been discovered that enhanced results are ob- 'tained when theworking mediumat the inlet channel is given a strong acceleration justbefore contacting the rotor blades. This is particularly true in caseswhere constructional limitations on the inlet channel may producevariable conditions or may not be completely compensated for by knownblade designs, and particularly with regard to the delaying or retardingeffect of Socalled dilfuser blades which are used in pumps andcompressorsv Thus, at the entrance to the blades, there may take placenot only a delay or retardation in axial direction of flow, butsimultaneously a circumferential turbulence to produce separation of theworking medium with attendant energy losses. Somewhat the same situationalso obtains with the stator conduits on the discharge side of therotor. Thus, the inlet channel of a compressor embodying this=inventionis produced with a gradually and constantly. diminishing cross sectionfor increased velocity and, in particular, is provided with a sudden andsubstantial jog: or constriction immediately before the rotor to-eifectsuch preliminary acceleration of the medium therein,

Furthermore, the flow. of the working medium upon discharge fromtheperiphery of a radialflow compressor rotor may not be uniform.O'nithe other hand, the energy conversion in the rotor may be morefavorable and more eflicient whenthcinlet flowv to the rotor. isuniform. By means of narrowing the cross section of; the dischargechannel between the rotor and thediffusion vanes, and the delay orretardation inthe original direction which occurs thereat, differencesnot. only in location but also in time between the velocities andpressures of individual stream linesare equalized.

Through the action of the whirling rotor, the medium receives a strongvelocity component in a circumferential direction, as well as the axialand radial components imparted to it by the blades. Thus, upon dischargefrom the rotor, the medium flows outwardly along spiral paths inindividual streams as created by the various rotor blades. Thiscircumferential velocity component diminishes, however, with increasingdistance from the axis of rotation and is, thus, inverselyproportional'to the radius. With diminishing velocity, accordingly, anenergy conversion obtains providing an increase of pressure and apressure gradient which increases radially outwardly as a result of thecircumferential velocity component and at least insofar as the radialvelocitycomponent is not correspondingly increased by constrictions orlessening of the flow channel area.

Thus, it has been discovered that the effective cross sectional area ofthe discharge channel can be so substantially reduced that the flowtherethrough' is substan tially rectilinear rather than spiral shapednotwithstanding the fact that the discharge channel is essentially acircular space surroundingthe rotor; Although anenergy conversion ofvelocity into' pressure is desired as a net and end result of compressoroperation, providinga discharge channel of'sufiiciently'diminishing areato'induce a rectilinear flow'immediatelybefore the diffusion vanes givesthe advantage that. the flow in eachindividual stream channel though thediffusion vanes is substantially as uniform as that in a straight ordirect diffuser.

For effective use, however, the rapidlymoving radially directedindividual streams may be collected in a common conduit and led to thecompressor outlet in the process of which the velocity energy should beconverted into pressure. According to this invention aspirally con guredcollecting channel is provided for this purpose. A conversion ofvelocity into pressure can, of course, take place merely by reason ofthe torsion or twist induced into the streams of compressed medium byleading them into and through a spiral channel, in which case thevelocity is diminished in an inverse proportion to the axis of rotation.Thus, a collectingQchannel laidjin a spiral channel has been found togive'better results when posiwith as great a diameter as possible mayprovide an increased efiiciency in the conversion of velocity intopressure, although it may alsolead to an impracticably large over-allcompressor size. On the other hand, reducing thev diameter andtightening the spiral in which the collectingchannelis disposed reducescompressor size but also decreases the. efliciency of the energyconversion particularly in view of'loss'es in drastically altering thedirection offiow.

Also, if the collecting channel be given a substantially circular crosssection so, that the so-called hydraulic radius of the cross section isat a minimum to provide a minimum energy loss as with a straightconduit, maximum efficiency is not obtained. Thus; with curved or spiralconduits, there are, in addition to the normal'fluid frictionedasymmetrically with respect to the direction of flow of the dischargingmedium from the rotor to the channel. Thus, with the cross sectionalareaof the collecting channel substantially bisected by the radial plane offlow of the medium from the rotor, the medium must be sharply deflectedonto'boththe two side-walls of the spiral channel upon entrythereinto ifthe cross section is to be keptwithin the-desiredradial'limits of-'size. By contrast, a compressor embodying the present invention has thespiral collecting channel offset axially from the radial plane throughwhichthe medium'fiows upon discharge of the rotor so that the-medium maybe led by a curved annular conduit into one side of the collectingchannel. foruniform and efiicientcollection. of the com.- pressed mediumall around the rotor andconversion of the high velocity energy thereinto additional pressure energy.

Referring to the drawing, which illustrates a compressor embodying thisinvention and constructed inaccordance with the. foregoing,the'rotorisshown as comprising a main rotor body 11 carrying thereonaplurality ofblades 11b and mounted on a' shaftlzthrough which the rotoris driven in known manner. The air or gas or other working medium to becompressed is sucked in an approximately axial directionithrough theinlet channel 13. The walls ofinlet channel 13 are supported by ribs 13band constantly converge so that the effective cross section thereofconstantly diminishes toward: the rotor 11, thereby inducing anaccelerating flow of the medium in channel 13. Just before the entranceto'the blades 11b there is provided an inwardly protruding'jogor'shoulder- 20 in the walls of channel 13' to effect a suddensubstantial further constriction of the cross sectional area of thechannel 13 and a consequent further rapid acceleration of the workingmedium immediately prior'to' contacting the blades 11b. Also, thissudden substantial constriction 20 effects an equalizing andstraightening out of the-individual flow stream-lines of the medium inchannel 13 with a concomitantly more favorable flow pattern intoand'through the blades 11b of the rotor 11.

After the whirling blades 11b have compressed and set in motion theworking medium, it' is discharged at the periphery of'the blades 11binto discharge channel 14 through which it moves rapidly in a spiralpath by virtue of the above mentioned circumferential and radialvelocity components imparted thereto by the blades 11b. The side wallsof discharge'channel 14 converge to provide a constantly diminishingcross section to effect further acceleration or velocity increase of thedischarge medium prior to the introduction thereof through thestationarystator diffusion blading 15. Although the walls of the discharge channel14 are shown as constantly converging, it may be desired'to have themsubstantially parallel throughout most of the extentlof channel .14 witha sudden substantial constriction immediately before the diffusion vanes15 in the same manner as with the inwardly protruding jog or shoulder 20in the inlet channel 13'.

The diffusion vane stator ring comprises angularly disposed divergingdiffusion vanes 15 mounted betweenrings 17 and'18 in the compressorhousingby means of fastening screws through the openings 19therein. Theaxial section of the diflusion vane ring tapers as does the dischargechanne114'and' the angular arrangement and divergence of the statorvanes 15 serve further for the conversion of velocity into pressure.

Thus, the flow of the working medium, after having been acted upon bythe blades 11b on rotor 11, is equalized and objectionable separationfrom the sidewalls of the channels is prevented. The noise inherent insuch radial flow compressors is, to a considerable extent, produced atthis point in channel 14 where the discharged highly compressed andrapidly moving medium impinges upon the diffusion vanes 15. Accordingly,in order to maintain this noise within unobjectionable limits as well asto provide for the desired energy conversion in the discharge channel14, the radial extent of channel 14 from the exit of the rotor blades11b to the entrance to the diffusion blades 15 is preferably.approximately ,5 of the outside diameter D of'the rotor 11 and theblades 11b thereon. i

As the working mediumpasses radially outwardly through diffusion vanes15, a rectification of the direction of flow results in the individualstream lines. Upon exiting from the radially outer side of diffusionvanes 15, the radially directed streams of flow are led by the curvedannular conduit 21 to the spiral collecting channel 16. Since the spiralchannel 16 is axially displaced from the radial plane of the dischargeside of blades 11b and diffusion ring 15 (i.e., the radial plane inwhich the various radially directed streams of compressing medium areflowing) a powerful energy conversion occurs upon the axial deflectionof the streams of flow by the curved annular conduit 21. Preferably theeffective axial width of conduit 21 from the exit of diffusion vanes 15to the entrance into the spiral collecting channel 16 is approximatelyequal to the axial width of diffusion ring 15 at the radially outer exitthereof.

As noted above, the spiral collecting channel 16 is provided with anoncircular cross section in which the axial dimension b is greater thanthe radial dimension Ar. Satisfactory results according to thisinvention have occurred when the axial dimension b of channel 16 wasapproximately 20% to 60% greater than the radial dimension Ar. Since thecross sectional area of channel 16 increases substantially constantlyalong the full length thereof, it will be understood that the foregoingdimensional relationships apply to the various diiferent axial andradial dimensions at different points along channel 16.

As noted above, channel 16 is disposed around the compressor essentiallyin the form of a spiral the inner diameter Di of which is preferably atleast as great as the radially inner diameter of diifusion vanes 15. Incompressors which do not include diifusion vanes 15, the inner diameterof the spiral configuration of collecting channel 16 is preferably atleast as great as the outer diameter of the rotor 11 with its blades11b.

Thus the compressed medium flows in a spiral path along the radiallyouter housing walls of conduit 21 and collecting channel 16 and returnsinwardly again after it has passed over a large part of thecircumference of channel 16 about the axis of rotation to achieve anincreased energy conversion at efficiencies hitherto regarded asunattainable while yet minimizing the over-all size of the compressorand its spiral collecting channel 16.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. In a radial flow gas compressor structure having an open-ended bladedrotor adapted to receive a gas to be compressed adjacent the center ofsaid rotor and to discharge said gas adjacent the periphery of saidrotor, the combination which comprises an inlet channel in saidstructure having a peripheral wall for supplying said gas to said rotor,the gross-sectional area of said inlet channel diminishingtoward saidrotor, an abrupt inwardjog in said peripheral wall of said inlet channeladjacent the intake of said rotor forming a sudden substantialconstriction in said inlet channel effecting an increased velocity insaid gas immediately prior to the intake of said rotor, a plurality ofdiffusion vanes in said structure disposed in an annulus around theperiphery of said rotor and radially spaced therefrom and defining anannular discharge channel between said rotor periphery and saiddiffusion vanes for conducting said gas discharged from the periphery ofsaid rotor to said diffusion vanes, the axial dimension of saiddischarge channel and said diffusion vanes diminishing radially outwardof saidrotor and said annular discharge channel and vanes beingcorrelated with the radial dimension thereof effecting substantialrectification of the flow lines of gas discharged from said rotor intosubstantially linear flow at said diffusion vanes, a spiral collectingchannel in said structure for receiving said gas from said diffusionvanes, said spiral channel being displaced axially of said rotor andsaid diffusion vane annulus in said structure, and a curved annularconduit said structure for conducting said gas from said diffusion vanesto said spiral collecting channel.

2. A radial flow gas'compressor according to claim 1 in which the radialdimension of said discharge channel from said rotor to said diffusionvane annulus is approximately one-tenth the diameter of said rotor andthe inner diameter of said spiral configuration of said collectingchannel is at least as great as the inner diameter of said diffusionvane annulus.

3. In a radial flow gas compressor structure having an open-ended bladedrotor adapted to receive a gas to be compressed adjacent the center ofsaid rotor and to discharge said gas adjacent the periphery of saidrotor, the combination which comprises an inlet in said structure havinga peripheral wall for supplying said gas to said rotor, thecross-sectional area of said inlet channel diminishing toward saidrotor, an abrupt inward jog in said peripheral Wall of said inletchannel adjacent the intake of said rotor forming a sudden substantialconstriction in said inlet channel effecting an increased velocity insaid gas immediately prior to the intake of said rotor, a plurality ofdiffusion vanes in said structure disposed in an annulus around theperiphery of said rotor and radially spaced therefrom and defining anannular discharge channel between said rotor periphery and saiddiffusion vanes for conducting said gas discharged at the periphery ofsaid rotor to said diffusion vanes, said vanes being angularly disposedwith respect to the axis of said rotor and diverging transaxiallyradially outwardly, the axial dimension of said discharge channel andsaid diffusion vanes diminishing radially outward of said rotor and saidannular discharge channel and vanes being correlated with the radialdimension thereof effecting substantial rectification of the flow linesof gas discharged from said rotor into substantially linear flow at saiddiffusion vanes, a spiral collecting channel in said structure forreceiving said gas from said diffusion vanes, said spiral channel beingdisplaced axially of said rotor and said diifusion vane annulus in saidstructure and a curved annular conduit in said structure for conductingsaid gas from said diffusion vanes to said spiral collecting channel.

4. In a radial flow gas compressor structure having an open-ended bladedrotor adapted to receive a gas to be compressed adjacent the center ofsaid rotor and to discharge said gas adjacent the periphery of saidrotor, the combination which comprises an inlet channel in saidstructure having a peripheral wall for supplying said gas to said rotor,the cross-sectional area of said inlet channel diminishing toward saidrotor, an abrupt inward jog in said peripheral wall of said inletchannel adjacent the intake of said rotor forming a sudden substantialconstriction in said inlet channel effecting an increased velocity insaid gas immediately prior to the intake of said rotor, a plurality ofdiffusion vanes in said structure disposed-in an annulus-aroundtheperipheryof'said-rotor and radially spaced therefrom and defining anannular discharge channel between said rotor periphery and saiddifiusion vanes forconducting gas discharged at the periphery of'saidrotor to said diffusion vanes; the axial dimension of saiddischarge-channel and said difiusion vanes diminishing radially outwardof said-rotor and being correlated with the radial dimension thereofefiecting substantial rectification of the flow lines of gas dischargedfrom said rotor into substantially linear flow at said diflusion vanes,a spiral collecting channel in said structure for receiving said gasfrom said diflusion vanes, said spiral channel being displaced axiallyof said'rotor and said diffusion vaneannulus in said'structure, a curvedannular conduit in said structure for conducting said gas from saiddiffusion vanes tosaid spiral collecting channel, the axial dimension ofthecross-sectionaharea of said spiral collectingchannel beinggreaterthan the radial dimension thereof, and the inner diameter of said spiralconfiguration of said collecting channel being at least as great as theinner diameter of said difi'usion vane annulus.

5. A radial flow gas compressor accordingtoclairn 4' in which saidspiral collecting channel is of constantly diminishing cross-section andthe axial dimension of cross-sections of said collecting channel areapproximately 20% to 60% greater'than the radial dimension thereof.

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